Communication networks that provide a common transport domain for use by multiple service domains and methods and computer program products for using the same

ABSTRACT

A method of operating a communication network comprises receiving loopback addresses from a plurality of edge networks at a provider router of a core backbone network, the edge networks and the core backbone network being logically distinct from each other, advertising the loopback addresses to a transport route reflector element, propagating the advertisement of the loopback addresses to other provider routers of the core backbone network using a protocol for communicating between autonomous systems, and using the transport route reflector element to advertise at least one of the loopback addresses to a service route reflector element in one of the plurality of edge networks.

RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/640,943, filed Dec. 17, 2009, the disclosure of which is herebyincorporated herein by reference as if set forth in its entirety.

BACKGROUND

The present disclosure relates generally to communication networks, and,more particularly, to methods, systems, and computer program productsfor providing a common transport domain for use by multiple servicedomains by divorcing the distribution of loopback addresses for nodereachability in the network from the signaling of the particularservice.

Some Interior Gateway Protocols (IGPs), such as Open Shortest Path First(OSPF), allow an Autonomous System (AS) network, for example, to bepartitioned into multiple areas to improve routing scalability withinparticular routing domains. Networks that use Multiprotocol LabelSwitching (MPLS) for routing, such as Virtual Private LAN Service (VPLS)networks, are required by the MPLS Label Distribution Protocol (LDP) todistribute loopback addresses for all Label Edge Routers (LERs) acrossall of the OSPF areas. Unfortunately, the deployment of a service thatrequires a large footprint of Provider Edges (PEs) may require manynon-zero AS areas to be defined. For example, implementation of a VPLSservice may create many non-zero areas that are aligned with thespecific metro area that a set of PEs are deployed in. As a result, thenumber of routers and Label Switch Paths (LSPs) may grow rapidly,possibly to the point that it may be difficult to scale the OSPF corebackbone area zero to support all of the non-zero areas.

SUMMARY

It should be appreciated that this Summary is provided to introduce aselection of concepts in a simplified form, the concepts being furtherdescribed below in the Detailed Description. This Summary is notintended to identify key features or essential features of thisdisclosure, nor is it intended to limit the scope of the disclosure.

Some embodiments provide a method of operating a communication networkcomprising receiving loopback addresses from a plurality of edgenetworks at a provider router of a core backbone network, the edgenetworks and the core backbone network being logically distinct fromeach other, advertising the loopback addresses to a transport routereflector element, propagating the advertisement of the loopbackaddresses to other provider routers of the core backbone network using aprotocol for communicating between autonomous systems, and using thetransport route reflector element to advertise at least one of theloopback addresses to a service route reflector element in one of theplurality of edge networks.

In other embodiments, the loopback addresses comprise Multi-ProtocolLabel Switching (MPLS) loopback addresses for labeled traffic andloopback addresses for non-labeled traffic.

In still other embodiments, advertising the loopback addresses comprisesassigning labels to the MPLS loopback addresses, respectively, andadvertising the labeled MPLS loopback addresses to the route reflectorelement.

In still other embodiments, advertising the loopback addresses comprisesadvertising the loopback addresses for non-labeled traffic using an OpenSystems Interconnection (OSI) reference model layer three protocol.

In still other embodiments, the core backbone network and the pluralityof edge networks are each distinct autonomous systems.

In still other embodiments, the core backbone network and the edgenetwork are configured to use an Interior Gateway Protocol (IGP) tocommunicate with one another.

In still other embodiments, the IGP comprises an Open Shortest PathFirst (OSPF) routing protocol.

In still other embodiments, the core backbone network comprises areazero of the OSPF routing domain and the edge networks comprise non-zeroareas of the OSPF routing domain.

In still other embodiments, the protocol for communicating betweenautonomous systems comprises a Border Gateway Protocol (BGP).

In still other embodiments, the loopback addresses have BGP communitiesattribute tags associated therewith.

In still other embodiments, propagating the advertisement of theloopback addresses to other provider routers of the core backbonenetwork is based on the BGP communities attribute tags associated withthe loopback addresses.

In still other embodiments, using the transport route reflector elementto advertise at least one of the loopback addresses to the service routereflector element in one of the plurality of edge networks is based onBGP communities attribute tags associated with the loopback addressesand the service.

In still other embodiments, the loopback addresses compriseMulti-Protocol Label Switching (MPLS) loopback addresses for labeledtraffic and loopback addresses for non-labeled traffic and at least oneof the loopback addresses advertised to the service route reflectelement comprises at least one of the loopback addresses for non-labeledtraffic.

In still other embodiments, using the transport route reflector elementto advertise at least one of the loopback addresses to the service routereflector element in one of the plurality of edge networks comprisesusing Border Gateway Protocol (BGP) to advertise at least one of theloopback addresses to the service route reflector element.

In still other embodiments, the core backbone network and the pluralityof edge networks use Multi-Protocol Label Switching (MPLS) as a routingprotocol and using the transport route reflector element to advertise atleast one of the loopback addresses to the service route reflectorelement in one of the plurality of edge networks comprises communicatingeach of the at least one of the loopback addresses to the service routereflect element as Next Hop Unchanged.

In still other embodiments, the core backbone network usesMulti-Protocol Label Switching (MPLS) as a routing protocol. The methodfurther comprises receiving an advertisement of a loopback addressassociated with the service route reflector element at the transportroute reflector element and propagating the advertisement of theloopback address associated with the service route reflector element tothe other provider routers of the core backbone network as Next HopeUnchanged using BGP.

In still other embodiments, propagating the advertisement of theloopback address associated with the service route reflector element tothe other provider routers of the core backbone is based on the BGPcommunities attribute tags associated with the loopback addressassociated with the service route reflector element.

In still other embodiments, the service comprises at least one ofVirtual Private LAN Service (VPLS) and Virtual Private Network (VPN).

In further embodiments, a communication network comprises a providerrouter in a core backbone network that is configured to receive loopbackaddresses from a plurality of edge networks, the edge networks and thecore backbone network being logically distinct from each other, and toadvertise the loopback addresses and a transport route reflector elementthat is configured to receive the advertisement of the loopbackaddresses and to propagate the advertisement of the loopback addressesto other provider routers of the core backbone network using a protocolfor communicating between autonomous systems and to advertise at leastone of the loopback addresses to a service route reflector element inone of the plurality of edge networks.

In other embodiments, a computer program product for operating acommunication network comprises a computer readable storage mediumhaving computer readable program code embodied therein. The computerreadable program code comprises computer readable program codeconfigured to receive loopback addresses from a plurality of edgenetworks at a provider router of a core backbone network, the edgenetworks and the core backbone network being logically distinct fromeach other, computer readable program code configured to advertise theloopback addresses to a transport route reflector element, computerreadable program code configured to propagate the advertisement of theloopback addresses to other provider routers of the core backbonenetwork using a protocol for communicating between autonomous systems,and computer readable program code configured to use the transport routereflector element to advertise at least one of the loopback addresses toa service route reflector element in one of the plurality of edgenetworks.

Other methods, systems, and/or computer program products according toembodiments of the invention will be or become apparent to one withskill in the art upon review of the following drawings and detaileddescription. It is intended that all such additional systems, methods,and/or computer program products be included within this description, bewithin the scope of the present invention, and be protected by theaccompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features of exemplary embodiments will be more readily understoodfrom the following detailed description of specific embodiments thereofwhen read in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram that illustrates a communication network thatincludes a core backbone network for use in distributing loopbackaddresses according to some embodiments;

FIG. 2 is a block diagram that illustrates operations of the routereflector element of FIG. 1;

FIG. 3 is a flowchart that illustrates operations for using a commontransport domain by one or more service domains in accordance with someembodiments;

FIG. 4 is a block diagram that illustrates Multiprotocol Label Switching(MPLS) label construction in communication networks according to someembodiments;

FIG. 5 is a block diagram that illustrates operations service domainsand transport domains according to some embodiments; and

FIG. 6 is a block diagram that illustrates a software/hardwarearchitecture for network elements that are configured to distributeloopback addresses in a communication network according to someembodiments.

DETAILED DESCRIPTION

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and will herein be described in detail. Itshould be understood, however, that there is no intent to limit theinvention to the particular forms disclosed, but on the contrary, theinvention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theclaims. Like reference numbers signify like elements throughout thedescription of the figures.

As used herein, the singular forms “a,” “an,” and “the” are intended toinclude the plural forms as well, unless expressly stated otherwise. Itshould be further understood that the terms “comprises” and/or“comprising” when used in this specification is taken to specify thepresence of stated features, integers, steps, operations, elements,and/or components, but does not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof. It will be understood that when anelement is referred to as being “connected” or “coupled” to anotherelement, it can be directly connected or coupled to the other element orintervening elements may be present. Furthermore, “connected” or“coupled” as used herein may include wirelessly connected or coupled. Asused herein, the term “and/or” includes any and all combinations of oneor more of the associated listed items.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andthis specification and will not be interpreted in an idealized or overlyformal sense unless expressly so defined herein.

Exemplary embodiments may be embodied as methods, systems, and/orcomputer program products. Accordingly, exemplary embodiments may beembodied in hardware and/or in software (including firmware, residentsoftware, micro-code, etc.). Furthermore, exemplary embodiments may takethe form of a computer program product comprising a computer-usable orcomputer-readable storage medium having computer-usable orcomputer-readable program code embodied in the medium for use by or inconnection with an instruction execution system. In the context of thisdocument, a computer-usable or computer-readable medium may be anymedium that can contain, store, communicate, propagate, or transport theprogram for use by or in connection with the instruction executionsystem, apparatus, or device.

The computer-usable or computer-readable medium may be, for example butnot limited to, an electronic, magnetic, optical, electromagnetic,infrared, or semiconductor system, apparatus, device, or propagationmedium. More specific examples (a nonexhaustive list) of thecomputer-readable medium would include the following: an electricalconnection having one or more wires, a portable computer diskette, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,and a portable compact disc read-only memory (CD-ROM). Note that thecomputer-usable or computer-readable medium could even be paper oranother suitable medium upon which the program is printed, as theprogram can be electronically captured, via, for instance, opticalscanning of the paper or other medium, then compiled, interpreted, orotherwise processed in a suitable manner, if necessary, and then storedin a computer memory.

According to some embodiments, loopback addresses of network elementslocated in edge networks of larger communication networks may bedistributed across the elements of a core backbone network without thoseloopback addresses appearing in the Interior Gateway Protocol (IGP)routing tables of the provider routers within the core backbone network.In particular, some embodiments use a protocol for communicating betweenautonomous systems, such as the Border Gateway Protocol (BGP), to carryloopback addresses from an edge network, across the core backbonenetwork, and to a destination edge network. In communication networksthat use Multiprotocol Label Switching (MPLS) for routing, thedistribution of loopback addresses may be carried out using the addressspace associated with the combination of BGP with an MPLS label. Thus,the core backbone network may be viewed as a transport autonomous systemfor use in distributing loopback addresses for reachability purposes.This may allow other edge network domains to operate as serviceautonomous system domains where the loopback address distribution isseparated from the signaling associated with the service itself. Such anapproach may allow for better control over route propagation andsignaling as well as improvements in overall scalability.

FIG. 1 illustrates an exemplary communication network 100, according tosome embodiments, in which a core backbone area zero 110 is connected totwo non-zero edge areas 120 a and 120 b. Although illustrated as a corearea zero 110 with two non-zero edge areas 120 a and 120 b, it will beunderstood that the embodiments described herein are not limited to sucha configuration. A core backbone network and associated edge networksmay be configured as part of a single Autonomous System (AS), but asseparate areas, such as, for example, when Open Shortest Path First(OSPF) is used as an Interior Gateway Protocol (IGP). In otherembodiments, the core backbone network and associated edge networks maybe configured to be separate ASes. Accordingly, in general, the corebackbone network and each edge network are configured to be logicallydistinct from one another.

Some embodiments will now be described by way of example with referenceto FIG. 1. In the FIG. 1 example, the core backbone area zero 110 may beimplemented as a BGP transport AS. The core backbone area zero 110includes two clusters of transport route reflector elements 125 a, 125b, 125 c, and 125 d. Route reflectors are used in BGP to act as a focalpoint for internal BGP sessions. Multiple BGP routers can peer with aroute reflector as a central point rather than peer with every otherrouter in a full mesh. The route reflector elements 125 a, 125 b, 125 c,and 125 d facilitate the distribution of loopback addresses from theedge areas 120 a and 120 b across the cross the core backbone area zero110 and to destination edge areas. The route reflector elements 125 a,125 b, 125 c, and 125 d may carry both Loopback0 and Loopback10addresses. Loopback0 addresses are used for non-MPLS labeled traffic andLoopback10 addresses are used for MPLS labeled traffic. While customertraffic is typically labeled in communication networks using MPLS, sometraffic may be non-labeled, such as network management traffic andcontrol plane functions. As a result, the route reflector elements 125a, 125 b, 125 c, and 125 d may support the Internet Protocol (IP)address space, such as IPv4 or IPv6, along with the address space basedon a combination of BGP with an MPLS label.

In the example shown in FIG. 1, route reflector elements 125 a and 125 bare dedicated to the western portion of the U.S. while route reflectorelements 125 c and 125 d are dedicated to the eastern portion of theU.S. The four route reflector elements 125 a, 125 b, 125 c, and 125 dmay be configured to disseminating both BGP/MPLS label routes along withIP, e.g., IPv4 routes. A route reflector in a given cluster isconfigured to have a multiprotocol internal BGP (MP-iBGP) session witheach of the route reflectors in the other cluster.

The provider routers (P routers) 130 a, 130 b, 130 c, and 130 d areconfigured to act as AS boundary routers to the respective edge areas120 a and 120 b and will each have an MP-iBGP session to each of theroute reflectors in the cluster to which the particular P router ishomed. Not all P routers in the core backbone area zero 110 need toestablish the MP-iBGP session because not all P routers will have edgeareas subtending them.

Each P router has a MP-iBGP session to both transport route reflectorsin the cluster for resiliency purposes. If one of the sessions fails forwhatever reason, the other route reflector in the cluster still hasaccess to all of the routes that are being disseminated. The BGP tableof the P router holds both sets of routes it receives from the two routereflectors. If a failure occurs with one of the two sessions, then theCisco Express Forwarding (CEF) table, and subsequently the ForwardingInformation Base (FIB), is updated. This generally should not have anyimpact on the packets being forwarded.

Operations for distributing loopback address information via a commontransport domain, such as the core backbone area zero 110 of FIG. 1,will now be described with reference to the network block diagram ofFIG. 2 and the flowchart of FIG. 3. At block 300 of FIG. 3, one or moreP routers receive loopback addresses from one or more edge networks(e.g., areas 120 a and 120 b of FIG. 1). The P router(s) will have theedge loopback addresses in its BGP routing tables. This may happen by,for example, a P router peering with an edge BGP speaker or byredistributing routes into BGP. In some embodiments, the loopbackaddresses have BGP communities attribute tags associated therewith whichcan be used as a basis for controlling the propagation and distributionof the loopback addresses throughout the network. As shown in theexample of FIG. 2, loopback addresses arrive into the P1 router table.These loopback addresses may include Loopback10 addresses so the P1router assigns labels to the addresses and, at block 310 of FIG. 3,advertises the loopback addresses and their labels to the transportroute reflector 210 using the BGP plus MPLS label address space. The P1router does not assign any label to Loopback0 addresses and mayadvertise the non-labeled loopback addresses to the transport routereflector 210 using, for example, an IPv4 unicast. The P1 router isadvertised as being the Next Hop (NH) for both Loopback0 and Loopback10addresses.

At block 320, the loopback address route advertisement is propagated toother P routers in the core backbone network that have a BGP sessionwith the route reflector 210, which is the P3 router in FIG. 3. Infurther embodiments, P routers may advertise the loopback addresses todestination edge networks as appropriate.

FIG. 4 illustrates examples of label construction in a common transportdomain, such as the core backbone area zero 110 of FIG. 1 according tosome embodiments. As data arrives at the P3 router from an edgenetwork/area, the bottom of the label stack includes the Service Label.An example of this label is the VPLS label signaled for a particularcustomer. On top of that label is the label that is used to get to P3.This label is present if P3 advertised itself as the Next Hop for thatdestination Provider Edge (PE) router into its locally connected edgearea. The P3 router will see the incoming top label and know that itneeds to swap the incoming label with the label it learned as being theNH. After swapping the labels, P3 will add the IGP label. The IGP labelis the LDP learned label that P3 will use to send traffic to P1.

Assuming that the P2 is the penultimate hop, as shown in FIG. 4, P2 willpop the top label and pass the packet on to P1. P1 will then see the toplabel as being the label that it advertised out. It will then perform aswap for the label that it knows is the label needed to continue sendingthe packet into the edge area.

As discussed above, the core backbone network may be viewed as atransport autonomous system for use in distributing loopback addressesfor reachability purposes. This may allow other edge network domains tooperate as effectively service AS domains where the loopback addressdistribution is separated from the signaling associated with the serviceitself. Various types of services may make use of common transportdomain, such as the core backbone area zero 110 of FIG. 1, including,but not limited to, Virtual Private LAN Service (VPLS) and VirtualPrivate Network services.

FIG. 5 illustrates the relationship between a service domain 500 and acommon transport domain 505. In particular, the service domain 500includes at least one service route reflector 510 and the commontransport domain 505 includes at least one transport route reflector 520as discussed above. Because the edge loopback addresses are in the BGProuting tables in the common transport domain 505, the service routereflector 510 uses BGP to acquire the ability to reach these routingnodes. Thus, the service route reflector 510 is shown to have a peerrelationship with the transport route reflector 520 using external BGP.Referring back to the flowchart of FIG. 3, at block 330, the transportroute reflector 520 advertise one or more of the loopback addresses tothe service route reflector 510.

Because the transport route reflector 520 could potentially be used toprovide reachability for different services, the advertisement of routesto a particular service route reflector may be based on BGP communitiesattribute tags associated with that particular service in someembodiments. The transport route reflector 520 only needs to advertisethe Loopback0 addresses of the PE devices to the service route reflector510 in some embodiments, as it is not expected that labeled traffic willbe sent from the service route reflector 510 to the PE devices in theedge networks/areas.

When the transport route reflector 520 advertises the edge loopbackaddresses to the service route reflector 510, they may be communicatedas Next Hop Unchanged. The service route reflector 510 needs to knowthat the “edge” P router is the next hop to get to the edge PE nodes.The service route reflector 510 knows how to get to the P router nexthop because they both reside in the same IGP domain.

The edge area devices may likewise need to know how to get to theservice route reflector 510. The particular manner in which this is donemay depend upon the way in which the edge networks/areas interface withthe core backbone network in accordance with various embodiments.Knowing that one of the options will be external BGP, the PE devices maylearn about the service route reflector 510 via BGP.

In some embodiments, the service route reflector 510 advertises itsLoopback0 address to the transport route reflector 520. The transportroute reflector 520 advertises the loopback address and Next HopUnchanged to the P routers with which it has a BGP relationship. The Prouter then advertises it into the edge network/area with the P router'sloopback now being the next hop. Again, this route propagation may bebased on may be based on BGP communities attribute tags associated withthe service route reflector's 510 loopback address.

Although FIGS. 1, 2, 4, and 5 illustrates exemplary communicationnetworks according to some embodiments, it will be understood that thepresent invention is not limited to such configurations, but is intendedto encompass any configuration capable of carrying out the operationsdescribed herein.

Although FIG. 1 illustrates an exemplary communication network, it willbe understood that the present invention is not limited to suchconfigurations, but is intended to encompass any configuration capableof carrying out the operations described herein.

FIG. 6 illustrates a processor 600 and memory 602 that may be used inembodiments of transport route reflectors, service route reflectors,and/or P routers as described above. The processor 600 communicates withthe memory 602 via an address/data bus 604. The processor 600 may be,for example, a commercially available or custom microprocessor. Thememory 602 is representative of the one or more memory devicescontaining the software and data used to mitigate email address harvestattacks and associated spam attacks in accordance with some embodiments.The memory 602 may include, but is not limited to, the following typesof devices: cache, ROM, PROM, EPROM, EEPROM, flash, SRAM, and DRAM.

As shown in FIG. 6, the memory 602 may contain up to five or morecategories of software and/or data: an operating system(s) 606, a BGPmodule 608, an IGP module 610, an MPLS module 612, a loopback addressadvertisement/reception module 614, and a loopback address propagationmodule 616. The operating system 606 generally controls the operation ofthe data processing system. In particular, the operating system 606 maymanage the data processing system's software and/or hardware resourcesand may coordinate execution of programs by the processor 600. The BGPmodule 608, IGP module 610, and MPLS module 612 may be configured tocarry out the operations associated with the respective communicationprotocols. The loopback address advertisement/reception module 614 maybe configured to advertise and/or receive loopback addresses with othernetwork elements, such as routers, devices, and the like. The loopbackaddress propagation module 616 may be configured to cooperate with theother communication protocol modules (608, 610, and 612) to manage thepropagation of loopback addresses between edge networks and a corebackbone transport network as described above. It will be understoodthat the various network elements, such as the transport routereflectors, service route reflectors, P routers, etc., may be configuredwith various ones of the modules 608, 610, 612, 614, and 616 inaccordance with different embodiments.

Although FIG. 6 illustrates exemplary hardware/software architecturesthat may be used in network elements, such as the transport routereflectors, service route reflectors, P routers, etc described above, itwill be understood that the present invention is not limited to such aconfiguration but is intended to encompass any configuration capable ofcarrying out operations described herein. Moreover, the functionality ofthe hardware/software architecture of FIG. 6 may be implemented as asingle processor system, a multi-processor system, or even a network ofstand-alone computer systems, in accordance with various embodiments ofthe present invention.

Computer program code for carrying out operations of data processingsystems discussed above with respect to FIGS. 1 and 2 may be written ina high-level programming language, such as Java, C, and/or C++, fordevelopment convenience. In addition, computer program code for carryingout operations of the present invention may also be written in otherprogramming languages, such as, but not limited to, interpretedlanguages. Some modules or routines may be written in assembly languageor even micro-code to enhance performance and/or memory usage.Embodiments described herein, however, are not limited to any particularprogramming language. It will be further appreciated that thefunctionality of any or all of the program modules may also beimplemented using discrete hardware components, one or more applicationspecific integrated circuits (ASICs), or a programmed digital signalprocessor or microcontroller.

Exemplary embodiments have been described herein with reference toflowchart and/or block diagram illustrations of methods, systems, andcomputer program products in accordance with exemplary embodiments.These flowchart and/or block diagrams further illustrate exemplaryoperations for mitigating email address harvest attacks and associatedspam attacks, in accordance with some embodiments. It will be understoodthat each block of the flowchart and/or block diagram illustrations, andcombinations of blocks in the flowchart and/or block diagramillustrations, may be implemented by computer program instructionsand/or hardware operations. These computer program instructions may beprovided to a processor of a general purpose computer, a special purposecomputer, or other programmable data processing apparatus to produce amachine, such that the instructions, which execute via the processor ofthe computer or other programmable data processing apparatus, createmeans and/or circuits for implementing the functions specified in theflowchart and/or block diagram block or blocks.

These computer program instructions may also be stored in a computerusable or computer-readable memory that may direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer usable orcomputer-readable memory produce an article of manufacture includinginstructions that implement the function specified in the flowchartand/or block diagram block or blocks.

The computer program instructions may also be loaded onto a computer orother programmable data processing apparatus to cause a series ofoperational steps to be performed on the computer or other programmableapparatus to produce a computer implemented process such that theinstructions that execute on the computer or other programmableapparatus provide steps for implementing the functions specified in theflowchart and/or block diagram block or blocks.

Many variations and modifications can be made to the preferredembodiments without substantially departing from the principles of thepresent invention. All such variations and modifications are intended tobe included herein within the scope of the present invention, as setforth in the following claims.

That which is claimed:
 1. A method, comprising: receiving loopbackaddresses from a plurality of edge networks at a provider router of acore backbone network, the edge networks and the core backbone networkbeing logically distinct from each other; advertising the loopbackaddresses to a transport route reflector element; propagating theadvertisement of the loopback addresses to other provider routers of thecore backbone network using a protocol for communicating betweenautonomous systems; and using the transport route reflector element toadvertise one of the loopback addresses to a service route reflectorelement in one of the plurality of edge networks; wherein the loopbackaddresses are not included in routing tables used by an interior gatewayprotocol for communication within the core backbone network; wherein thecore backbone network and the edge network communicate with one anotherusing the interior gateway protocol; and wherein the autonomous systemscommunicate using a border gateway protocol.
 2. The method of claim 1,wherein the loopback addresses comprise multi-protocol label switchingloopback addresses for labeled traffic and loopback addresses fornon-labeled traffic.
 3. The method of claim 2, wherein advertising theloopback addresses comprises: assigning labels to the multi-protocollabel switching loopback addresses, respectively; and advertising thelabeled multi-protocol label switching loopback addresses to the routereflector element.
 4. The method of claim 2, wherein advertising theloopback addresses comprises: advertising the loopback addresses fornon-labeled traffic using an open systems interconnection referencemodel layer three protocol.
 5. The method of claim 1, wherein the corebackbone network and the plurality of edge networks are each distinctautonomous systems.
 6. The method of claim 1, wherein the interiorgateway protocol comprises an open shortest path first routing protocol.7. The method of claim 6, wherein the core backbone network comprisesarea zero of the open shortest path first routing domain and the edgenetworks comprise non-zero areas of the open shortest path first routingdomain.
 8. The method of claim 1, wherein the loopback addresses haveborder gateway protocol communities attribute tags associated therewith.9. The method of claim 8, wherein propagating the advertisement of theloopback addresses to other provider routers of the core backbonenetwork is based on the border gateway protocol communities attributetags associated with the loopback addresses.
 10. The method of claim 8,wherein using the transport route reflector element to advertise the oneof the loopback addresses to the service route reflector element in oneof the plurality of edge networks is based on border gateway protocolcommunities attribute tags associated with the loopback addresses andthe service.
 11. The method of claim 1, wherein the loopback addressescomprise multi-protocol label switching loopback addresses for labeledtraffic and loopback addresses for non-labeled traffic and wherein theone of the loopback addresses advertised to the service route reflectorelement comprises one of the loopback addresses for non-labeled traffic.12. The method of claim 1, wherein using the transport route reflectorelement to advertise the one of the loopback addresses to the serviceroute reflector element in one of the plurality of edge networkscomprises using the border gateway protocol to advertise the one of theloopback addresses to the service route reflector element.
 13. Themethod of claim 12, wherein the core backbone network and the pluralityof edge networks use multi-protocol label switching as a routingprotocol and wherein using the transport route reflector element toadvertise the one of the loopback addresses to the service routereflector element in one of the plurality of edge networks comprisescommunicating each of the one of the loopback addresses to the serviceroute reflector element as next hop unchanged.
 14. The method of claim1, wherein the core backbone network uses multi-protocol label switchingas a routing protocol, the method further comprising: receiving anadvertisement of a loopback address associated with the service routereflector element at the transport route reflector element; andpropagating the advertisement of the loopback address associated withthe service route reflector element to the other provider routers of thecore backbone, network as next hop unchanged using the border gatewayprotocol.
 15. The method of claim 14, wherein propagating theadvertisement of the loopback address associated with the service routereflector element to the other provider routers of the core backbonenetwork is based on the border gateway protocol communities attributetags associated with the loopback address associated with the serviceroute reflector element.
 16. The method of claim 1, wherein the servicecomprises one of a virtual private LAN service and a virtual privatenetwork.
 17. A system, comprising: a processor; and a computer readablemedium that comprises computer readable program code that when executedby the processor causes the processor to perform operations comprising:receiving loopback addresses from a plurality of edge networks at aprovider router of a core backbone network, the edge networks and thecore backbone network being logically distinct from each other;advertising the loopback addresses to a transport route reflectorelement; propagating the advertisement of the loopback addresses toother provider routers of the core backbone network using a protocol forcommunicating between autonomous systems; and using the transport routereflector element to advertise one of the loopback addresses to aservice route reflector element in one of the plurality of edgenetworks; wherein the loopback addresses are not included in routingtables used by an interior gateway protocol for communication within thecore backbone network; wherein the core backbone network and the edgenetwork communicate with one another using the interior gatewayprotocol; and wherein the autonomous systems communicate using a bordergateway protocol.
 18. A computer program product, comprising: anon-transitory computer readable storage medium having computer readableprogram code embodied in the medium that when executed by a processorcauses the processor to perform operations comprising: receivingloopback addresses from a plurality of edge networks at a providerrouter of a core backbone network, the edge networks and the corebackbone network being logically distinct from each other; advertisingthe loopback addresses to a transport route reflector element;propagating the advertisement of the loopback addresses to otherprovider routers of the core backbone network using a protocol forcommunicating between autonomous systems; and using the transport routereflector element to advertise one of the loopback addresses to aservice route reflector element in one of the plurality of edgenetworks; wherein the loopback addresses are not included in routingtables used by an interior gateway protocol for communication within thecore backbone network; wherein the core backbone network and the edgenetwork communicate with one another using the interior gatewayprotocol; and wherein the autonomous systems communicate using a bordergateway protocol.